The SHPP Transconductance
.
Refer to the wiring diagram for the SHPP in the description pdf.
You should permanently solder a pair of 2W 10R resistor between S & O (see photo).
Connect 50R dummy load between S and G.
Connect both G to 0V of the aux supply (+/-24V) (for testing only).
Then connect a 1k resistor to S.
Apply a functions generator with 5~10V sine wave at 100Hz with initially 0V DC offset.
Nothing should happy, and the relay show go on after a slow start delay.
Increase the DC offset of the func gen slowly, to about 1.06V.
The trigger should then occur.
This then corresponds to a DC current of 1.06V / (1k + 10R + 50R) ~ 1mA.
The AC signal should have no effect when DC is not present.
Check DC offset in both directions and for both channels.
The SHPP Trans is primarily designed to work with SL Trans in current mode only.
In principle it can work in both current and voltage modes.
But the 10R current sensing resistor in the SHPP will increase the Zout by 10R.
AND you need to limit the power supply current to 300mA in the regulators.
When the SHPP Trans triggers the amp is loaded by Rs only and hence you must have current limit somewhere.
The other simple way around is to change Rs to 5.1R, and accept 2mA DC current (0.1V DC for 50R load).
Then the current limit of 600mA is still OK.
Patrick
.
.
Refer to the wiring diagram for the SHPP in the description pdf.
You should permanently solder a pair of 2W 10R resistor between S & O (see photo).
Connect 50R dummy load between S and G.
Connect both G to 0V of the aux supply (+/-24V) (for testing only).
Then connect a 1k resistor to S.
Apply a functions generator with 5~10V sine wave at 100Hz with initially 0V DC offset.
Nothing should happy, and the relay show go on after a slow start delay.
Increase the DC offset of the func gen slowly, to about 1.06V.
The trigger should then occur.
This then corresponds to a DC current of 1.06V / (1k + 10R + 50R) ~ 1mA.
The AC signal should have no effect when DC is not present.
Check DC offset in both directions and for both channels.
The SHPP Trans is primarily designed to work with SL Trans in current mode only.
In principle it can work in both current and voltage modes.
But the 10R current sensing resistor in the SHPP will increase the Zout by 10R.
AND you need to limit the power supply current to 300mA in the regulators.
When the SHPP Trans triggers the amp is loaded by Rs only and hence you must have current limit somewhere.
The other simple way around is to change Rs to 5.1R, and accept 2mA DC current (0.1V DC for 50R load).
Then the current limit of 600mA is still OK.
Patrick
.
Attachments
Last edited:
Plugging and unplugging the phone
.
During power off the positive and negative sides do not switch off 100% synchronous.
As a result, the headphone will see an offset current if not unplugged beforehand.
So turn down the music first, then unplug before power off, and I had no issues.
Best to install an additional manual switch in series with the protection relay LED & resistor (R20).
Switch open will close the protection relay contacts which will then enable safe plug and unplug at any time.
I highly recommend you do this, especially if you are using TRS (3.5 or 6.35).
If in doubt, ask first.
And test it with a cheap 300R phone in parallel with a 50R dummy resistor (to simulate a 50R phone).
Only when you are happy that everything works as intended, then use your planar magnetics.
Keep you busy during X'mas. 😉
Patrick
.
During power off the positive and negative sides do not switch off 100% synchronous.
As a result, the headphone will see an offset current if not unplugged beforehand.
So turn down the music first, then unplug before power off, and I had no issues.
Best to install an additional manual switch in series with the protection relay LED & resistor (R20).
Switch open will close the protection relay contacts which will then enable safe plug and unplug at any time.
I highly recommend you do this, especially if you are using TRS (3.5 or 6.35).
If in doubt, ask first.
And test it with a cheap 300R phone in parallel with a 50R dummy resistor (to simulate a 50R phone).
Only when you are happy that everything works as intended, then use your planar magnetics.
Keep you busy during X'mas. 😉
Patrick
Patrick would 1 watt resistors be ok for R15/16 - What is the current through these?
I have Dale CMF60 1W 39.2R in the stash is all.
I have Dale CMF60 1W 39.2R in the stash is all.
Thanks Patricks
I think probably january... German DHL is quite overloaded 😔
But january is OK
Hello Patrick,
boards arrived today. So my project for 2019 is save now 🙂
Best wishes for 2019 and thanks a lot.
Arnd
boards arrived today. So my project for 2019 is save now 🙂
Best wishes for 2019 and thanks a lot.
Arnd
Any plans for more PCBs for this, Patrick? Recently purchased the Audeze LCD-3 so am interested in trying this out.
Got a pair of Dan Clarke Audio Aeon 2 and have been looking for which amp to build for them and this seams like the perfect fit.
So let me know when/if there are any boards that needs a home.
So let me know when/if there are any boards that needs a home.
I’ve had the pleasure to enjoy the Super Linear Transconductance headphone amp for many months now since Patrick kindly sent his build for me for listening test. During these few months it has proven to be an excellent companion for my Audeze LCD-2 (phazor) planar headphones.
The SL Trans is now my new reference headamp so it is highly recommended if you happen to have planar headphones to pair it with.
Actually I like it so much that I refused to send it back to Patrick...😀
The SL Trans is now my new reference headamp so it is highly recommended if you happen to have planar headphones to pair it with.
Actually I like it so much that I refused to send it back to Patrick...😀
😉
You are actually the second person I know who declared it as reference for planar magnetic phones.
Patrick
You are actually the second person I know who declared it as reference for planar magnetic phones.
Patrick
